We thought that when it came to the human body, there were no more uncharted territories. And yet, a new study has revealed the discovery of a potential organ which previously had not been discovered, known as the interstitium. This structure, the largest in the human body, plays a vital role in the function of organs, most of our tissues, and perhaps even in the mechanisms of many diseases.Compartments that protect the bodyUntil now taken for a layer of collagen, the interstitium has turned out to be something else. Located beneath our epidermis, covering the digestive tract, lungs, urinary system, surrounding arteries, veins and the fascia that surrounds our muscles, it consists of inter-connected compartments that are filled with fluid.These compartments are structured by a network of connective tissue-forming proteins, consisting of collagen (which is rather rigid) and elastin (which is more flexible). They most likely play a role in shock absorption, so that the tissues don’t tear during the daily activities of the muscles, veins and other organs. They are also lymph producers and could play a role in the appearance of wrinkles and various symptoms related to old age.Far from being closed walls, the tissues that compartmentalise these pockets circulate fluids, making the interstitium a true liquid highway. This property could help us to understand how cancers spread. Indeed, anything that attacks the interstitium is much more likely to spread, probably through the use of this ‘highway.’A late discoveryIt is only by chance that this new potential organ was discovered in an observation using the recent confocal endomicroscopy technique on a patient with cancer. During this examination, the doctors observed a set of cavities whose existence had never been seen before. They then decided to conduct further analyses that revealed how the interstitium could have escaped their radar for so long.During an observation using a microscope, the sample had to be ‘kept in place’ using chemical treatments and dyes. These did indeed reveal the solid structures but eliminated any liquid traces. In the absence of fluids, the protein microarchitecture that forms the pockets of the interstitium collapses and it becomes impossible to observe the organ as it appears in the human body. We find ourselves facing a set of ruins out of which it is impossible to make sense.In their new study, the researchers at the origins of the discovery have suggested to make the interstitium the 80th organ in the human body. This new concept has revolutionised our understanding of this interstitial space, which until now has had a relatively nebulous concept in anatomy. It could also provide us with invaluable keys to the way we approach the treatment of diseases. But its status as a real organ remains to be confirmed. In the meantime however, we can always welcome potential organ # 80!Take a look at the video above for more on the interstitium!